The following description of the prior art is not intended to be, nor should it be interpreted as, an indication of the common general knowledge pertaining to the invention.
A common problem faced in off-road applications is that the tire bead may become separated from the wheel rim when operating the vehicle at low tire pressures. Particularly in off-road applications, the tires are commonly subjected to substantial lateral forces and, without reinforcement, a standard tire bead may become disassociated from the wheel rim. This is particularly so in off-road racing, extreme off-road conditions or where very low tire pressures are involved.
Another issue involves use of low profile tires. In such tires the space between road hazards such as small solid objects and the wheel rim is small and may lead to rim damage where the object can make a damaging impact on the rim. Moreover, the difference between an inflated low profile tire and an unintentionally deflated tire may be minimal and leave the driver unaware of the deflated condition of a tire (particularly on a rear wheel, also leading to rim damage or tire side wall damage or both).
In the trucking industry a common technique employed where greater tire traction is required is to partially deflate the tires. Such situations may arise on muddy work sites or where heavy vehicles such as timber jinkers are required to travel along unmade roads. One hazard in such applications is that the tire bead of one of the tires may become disassociated with its wheel rim.
A number of bead lock type devices have been proposed. For example, the Tireloc (Reg™) bead lock system includes an inner casing interposed between the inner surface of a pneumatic tire and the rim and encloses a small inner tube. The inner tube is inflated so that the inner casing bears against the inner surface of the tire bead, thereby locking it against the wheel rim. One advantage of such a system is that, in the event of a puncture, the wheel may still be serviceable to the extent that the inner casing arrangement protects tire from being damaged by the wheel rim. Moreover, and more particularly for off-road applications, the pneumatic tire may be deflated to substantially increase the traction of the tire whilst maintaining the inner tube in a fully inflated condition to protect the tire bead against the wheel rim and to retain the tire bead on the wheel rim.
The Tireloc system includes a solid rubber plate with longitudinal grooves to enable the inflation of the pneumatic tire. This solid rubber plate is relatively heavy and may require wheel balancing to compensate. Although the solid rubber plate is partially flexible, it is insufficiently flexible to follow the contours of the wheel rim without, over time, suffering fatigue and eventual breakage, thereby requiring costly and inconvenient replacement. In addition, these components are relatively expensive to manufacture and it is therefore desirable that a cheaper alternative be available.